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5/31/2010 - 6/6/2010

CCA Credit Opportunity on June 24

Jim Fawcett, ISU Extension Field Agronomist

Certified crop advisers (CCAs) can earn five hours of credit – three hours in soil and water management, one in pest management, 0.5 each in crop management and nutrient management – by attending a special CCA morning session and the Southeast Iowa Research and Demonstration Farm spring field day tour June 24. The morning session and field day will be at the ISU research farm near Crawfordsville.

The morning session will begin at 9 a.m. with a presentation by Matt Helmers, ISU Extension ag engineer, on “How do we design subsurface drainage systems considering crop production and water quality?” Other morning presentations will include a demonstration on “Goof plots – herbicide injury symptoms” by Jim Fawcett, ISU Extension field agronomist; and a presentation by Emily Heaton, ISU agronomist, on “Environmental impacts of perennial energy crops.”

The afternoon tour will include: Crop Season Review & Soil Drainage Research Results by Kevin Van Dee, farm superintendent and Helmers; Cover Crops & Nitrogen Management, by John Sawyer, ISU Extension agronomist; Research on Miscanthus and Other Crops for Cellulosic Ethanol, by Heaton; and New Developments in Soybean Aphid Management, by Erin Hodges, ISU Extension entomologist. Tours will begin at 1 p.m.

Pre-registration should be completed by June 22 to avoid a $20 late fee. To pre-register call the Johnson County Extension Office at 319-337-2145 or send an e-mail note to Jim Fawcett at The registration fee of $50, which includes lunch, can be paid at the door. Registration for CCAs will begin at 8:30 a.m.

To reach the research farm go 1 3/4 miles south of Crawfordsville on Highway 218, then 2 miles east on G-62, then 3/4 mile north.


Jim Fawcett is an Iowa State University Extension field crops specialist serving eastern Iowa counties.

Curious Cutworms in Soybean Fields

Erin Hodgson, Department of Entomology

In the last two weeks, I've heard reports of cutworm damage in soybean. Rich Pope visited a commercial soybean field in Harrison County and identified a mixture of black cutworm and dingy cutworm (Fig. 1). Matt O'Neal, ISU soybean entomologist, confirmed cutworm damage in soybean research plots at Curtiss Farm just south of Ames in Story County. The small cage plots were also infested with a combination of cutworm species (Fig. 2). It can be difficult to distinguish cutworm species without a hand lens, but a previous ICM article can help with identification

Fig 1. A field in Harrison County, Iowa showing 50-60 percent stand loss due to cutworms. Photo by Rich Pope.

Fig 2. Cutworms found in Story County, Iowa.

Cutworm damage in corn is reported almost every year in Iowa. But infestations are patchy and sporadic because they have to migrate here every spring. On the other hand, cutworm damage in soybean is not typical. The last time cutworm damage was reported in ICM News was in 1999 by Marlin Rice. Entomologists don't fully understand why cutworms sometimes cause damage to soybean. However, there are a few field conditions that may make soybean fields attractive to female cutworm moths:
• Fields planted under reduced or no-tillage practices
• Fair to poorly drained fields
• Fields with winter annual weeds emerged prior to soybean planting
• More likely found in fields previously infested with cutworms

Economic thresholds have not been developed because infestations are unpredictable and infrequent. Treatment decisions must be based on the size of the cutworms and level of infestation. In some cases of very heavy cutworm density, fields may have to be replanted. Check 20 consecutive plants in five different areas of the field to determine percent cutworm damage. Young cutworms may feed on the stem or leaves, but older larvae can clip off the cotyledons. Also, look for discolored, wilted or dead plants. Cutworms will seek shelter during the day, so dig 2-3 inches down in the soil within a row. Consider an insecticide if larvae are less than 3/4 inch long and more than 20 percent of plants are damaged or missing.



Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at or phone (515) 294-2847.

Characteristics of Corn Left Standing Through Winter 2009-2010 in Iowa

Alison Robertson and Gary Munkvold, Department of Plant Pathology; Charles Hurburgh, Department of Agricultural and Biosystems Engineering

Very wet conditions in October 2009 and early snowfalls in November resulted in several thousand acres of corn left standing through the winter in Iowa. Considering the grain quality issues that ended the growing season, concerns were raised regarding the quality of corn left standing over the winter. 

To address these concerns, samples of ears were collected from 72 fields throughout Iowa in March 2010. Ears were visually assessed for ear rot severity. After shelling, test weight, moisture, protein, oil, starch and density were determined before grain was ground and tested for deoxynivalenol (DON), zearalenone (ZEA) and fumonisins (FUM) using GIPSA-approved commercially available antibody-based lateral flow strip tests.

Ear rot severity (percentage of ear covered with mold), physical characteristics and mycotoxin contamination were compared with ear samples collected in October 2009 from 27 arbitrarily selected Iowa fields. These fields were part of the 2009 Iowa Hail Damage Grain Quality Survey and were considered representative of undamaged corn grain at the end of the 2009 growing season.    

Mean ear rot severity among standing corn fields ranged from 0.2 to 83.8 percent (Table 1). Ear rot severity in standing corn (24.0 percent) was statistically greater than ear rot severity in October 2009 (3.3 percent).  The predominant ear rot in standing corn was Cladosporium, followed by Fusarium and Gibberella at low levels, which is similar to ear rots present on corn in October 2009. 

Not surprisingly, range in test weight of the standing corn was similar to that of corn in October 2009, and grain moisture was significantly lower in standing corn (18.4 percent) compared with grain moisture in October 2009 (24.4 percent) (Table 1).

Low levels of fumonisin (0.1 ppm), DON (0.9 ppm) and zearalenone (0.72 ppm) were detected in grain from standing corn and these levels of mycotoxins were not statistically different from those detected in grain sampled in October 2009 (Tables 1).

Grain that remained in the field actually fared better than grain stored in bins over the winter. Although severity of Cladosporium ear rot was high, most growers reported that “the mold blew off in the combine” and grain quality was good.  These findings may create viable alternatives to ground piles for wet corn volumes beyond dryer capacity at elevators.

We thank ISU Extension field agronomists for collecting ear samples, and growers who allowed us to sample their fields. We also thank Agribusiness Association of Iowa, ISU College of Agriculture and Life Sciences, and Iowa State University Extension who provided funding to cover costs associated with this survey.





Alison Robertson is an assistant professor of plant pathology with research and extension responsibilities in field crop diseases. Robertson may be reached at (515) 294-6708 or by email at Gary Munkvold is an associate professor of plant pathology and seed science endowed chair in the Iowa State University Seed Science Center with research and teaching responsibilities in seed pathology. He can be reached at (515) 294-7560 or by email at Charles Hurburgh is an agricultural and biosystems engineering professor who manages the Grain Quality Research Laboratory and the extension-based Iowa Grain Quality Initiative. He can be contacted at (515) 294-8629 or by email at

ISU Weed Science Field Day

Iowa State University Weed Science will hold the annual Weed Science Field Day on June 24 at 8:30 a.m. at the Curtiss Farm on South State Street, Ames, Iowa. Registration for the field day is $20 and includes coffee, beverages, snacks and a field book.  If you have questions about the event, please contact Mike Owen at or 515-294-5936.

Scouting for Soybean Seedling Diseases

By X.B.Yang and SS. Navi, Department of Plant Pathology

Seedling diseases are one reason to use seed treatment. Each planting season, different weather patterns result in different seedling disease problems. This planting season has been smooth in general and seedlings have emerged in many soybean fields. So far, disease risk is lighter than last year. We did, however, observe some light occurrence of seedling disease from production fields around the central Iowa. Damping-off was also found in our research plots. It is now time to check your soybean fields to determine if there are any seedling disease problems.

With weather conditions better than last planting season, we should see less disease problems, especially in fields treated with fungicides. If you find significant seedling diseases in a field planted with treated soybean seeds, you should reconsider the seed treatment you used.  Knowing what disease causes the problem is critical to correcting the problem in the next planting.

This year, seedling diseases caused by three fungi are likely to be found, Pythium, Rhizoctonia, and Phytophthora. For fields that planted early in cool soil, Pythium damping-off is the most likely to be found, as we did last week. In most of years, this is the first disease found in a growing season because the fungus prefers cold soil temperatures. Dead seedlings may be visible on the ground with infected plants killed before the first true leaf stage. Plants often have a rotted appearance. Leaves of infected seedlings are initially gray-green and then turn brown. A few days later, the plants die. Diseased plants are easily pulled from the soil because of rotted roots.

The symptoms of Phytophthora is similar to Pythium and can be mistaken for Pythium damping-off. Phytophthora is more likely to infect soybean plants in later planted soybean because the fungus prefers warm soil temperatures and high soil moisture. 

Another disease that may be found in later plant soybean this year is Rhizoctonia damping-off. Caused by Rhizoctonia fungus, this disease likes soil temperatures warmer than that for Pythium. Soybean seedling disease caused by Rhizoctonia exhibit symptoms different from those caused by Phytophthora. Unlike Phytophthora damping-off, stem discoloration by Rhizoctonia is usually limited to the cortical layer of the main root and hypocotyl. Infected stems remain firm and dry. Typical symptoms are localized brown-to-reddish brown lesions on the hypocotyl. Root rot is visible on severely infected plants. 

Seedling disease risk differs from field to field. River bottom fields are more likely to have Pythium and Rhizoctonia, sandy soil is more likely to have Rhizoctonia, and Phytophthora is more likely to occur in heavy soils. Within a field, some spots are more likely to have seedling disease than other areas. To quickly spot the disease problems, you can check areas or fields that are most likely to have disease problems. Seedling diseases usually occur first in low spots with higher soil moisture, in areas with poor drainage or in compacted areas. 

Damping off of soybean seedling caused by Pythium (Photo credit: SS Navi)


XB Yang is a professor of plant pathology with responsibility in research and extension. SS Navi is assistant scientist working on soybean diseases. Yang can be contacted by email at or by phone at (515) 294-8826.

Research and Demonstration Farm 2010 Field Days Scheduled

By Adam Sisson, Corn and Soybean Initiative

Iowa State University Research and Demonstration Farm spring and summer field days are a chance to see research projects in progress and talk with the researchers involved in the experiments. They also provide the opportunity to view the latest in modern agriculture. Topics covered during the 2010 field days will include nitrogen fertilization, aphid resistant soybean varieties, GPS equipment and cellulosic ethanol. 

ISU Research and Demonstration Farms field days are free of charge and open to the public. Events will take place regardless of weather. Those attending field days at Iowa State farms with livestock - Armstrong and Neely-Kinyon - are asked to take the following precautions.

The following livestock policies apply to research and demonstration farms marked by an asterisk (*).
• Those who have recently returned from a trip abroad are asked to wait five days before visiting Iowa State farms with animals.
• Change clothing and footwear before attending field days if another farm with livestock has been visited.
• Refrain from bringing any food items to the research farm.
• Visitors with further questions are asked to call the Research and Demonstration Farms office at (515) 294-5045 or read the Foot and Mouth Advisory (135K PDF).

2010 Field Day Schedule

Armstrong Research and Demonstration Farm,*  near Lewis 
June 16, 9:30 a.m.
Topics include miscanthus as a potential biomass crop, Western corn rootworm and Bt corn, switchgrass use in wide buffer strips and nitrogen fertilization of corn and cover crops

Southeast Research and Demonstration Farm, near Crawfordsville
June 24, 1 p.m.
Topics include nitrogen management and cover crops, soybean aphids, soil drainage and cellulosic ethanol

Northern Research and Demonstration Farm, Kanawha
June 29, 9:30 a.m.
Topics include GPS equipment, soybean diseases and current crop topics

Muscatine Island Research and Demonstration Farm,  Fruitland
June 29, 1 p.m  (lunch at noon)
Topics include 75th anniversary celebration, biodegradable mulch, subsurface drip irrigation, sweet corn herbicides, Colorado potato beetle management and weather and crop updates

Northwest Research and Demonstration Farm, near Sutherland
June 30, 9:30 a.m.
Topics include tillage and P and K fertilizer, corn rootworm management, tiling demonstration and crop update

Northeast Research and Demonstration Farm, near Nashua
June 30, 1 p.m.
Topics include weed management, foliar fungicide for corn and soybeans, nitrogen fertilizer, biofilters and aphid resistant soybean varieties

Neely-Kinyon Research and Demonstration Farm, * near Greenfield Aug. 25, 4 p.m.
Topics include long-term organic crop rotation study, corn disease and soybean aphid management

Northeast Research and Demonstration Farm, near Nashua
Aug. 26, 1:30 p.m. 
Topics include crop production

Northwest Research and Demonstration Farm, near Sioux City
Sept. 1, 5:30 p.m., Dordt College northern farm
Topics include strip tillage and on-farm research

Northern Research and Demonstration Farm, Kanawha
Sept. 9, 9:30 a.m.
Topics include crop production

Southeast Research and Demonstration Farm, near Crawfordsville
Sept. 15, 1 p.m.
Topics include manure injection

Additional information, including the field day brochure and directions to the research and demonstration farms, is available from the research and demonstration farm field day website.

This article was published originally on 6/7/2010 The information contained within the article may or may not be up to date depending on when you are accessing the information.

Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.